Our past studies in model systems, in vitro, have shown that specific salivary proteins, adsorbed onto synthetic hydroxyapatite (HA), selectively promote adhesion of several prominent oral bacterial species to HA. These findings strongly suggest that specific salivary proteins, adsorbed onto teeth, may play an important role in the highly selective initial adhesion of oral bacteria that occurs naturally on tooth surfaces. It is now important to test this hypothesis, in vivo. To make this test, and to advance knowledge in this area, the following aims are proposed. AIM 1 To test the central hypothesis that specific salivary proteins, adsorbed onto dental enamel surfaces, promote selective bacterial adhesion to those surfaces, in vivo. Pure samples of selected salivary proteins, known to promote adhesion of prominent oral bacteria to HA in vitro, will be used to treat enamel blocks. The blocks will be mounted on a prosthetic device, and the device placed in the mouth. The initial adhesion of selected bacteria to the protein-treated enamel will be determined over several hours in eight subjects by combined cultural and DNA checkerboard analyses using 16S rRNA probes. The microbial adhesion data will be analyzed statistically for relationships with the protein pretreatments. AIM 2 j To test the hypothesis that a subject's salivary protein profile determines pellicle composition, and that this influences selective bacterial adhesion to dental enamel in vivo. Salivary composition is poorly defined. Therefore, adsorption of specific bacterial adhesion-promoting proteins onto HA will be quantified, in vitro, for the eight subjects used in Aim 1, using techniques developed for that purpose. Thus, the amounts of the different adhesion-promoting proteins adsorbing onto the mineral will be determined. Each subject's microbial adhesion data, obtained in Aim 1, will be analyzed statistically for relationships with the same subject's salivary protein profile and protein adsorption data. AIM 3 To test the hypothesis that some salivary and serum proteins and bacterial macromolecules such as glucans and glycosyl-transferases act as inhibitors of adhesion of specific oral bacteria to HA-adsorbed salivary proteins. The possible role of some salivary and serum proteins and selected bacterial products as inhibitors of initial microbial adhesion is a further important activity that must be systematically quantified to understand selective microbial adhesion to teeth, in vivo. Therefore, the effects of chromatographic fractions from saliva and serum, and the noted bacterial macromolecules, on specific bacteria-salivary protein adhesion reactions will be determined, in vitro, As appropriate, these data will be incorporated into the interpretation of results of Aim 1.